Unhappy about information coming out of Mt.Gox about recent withdrawal problems, Mr. Burges, a London resident, this week bought a last-minute ticket to Tokyo for 850 pounds (around $1,400) to get better answers. He arrived in Japan on Wednesday and requested an appointment with Tibanne executives. He received no reply, he said, and thus showed up to protest at the offices of the exchange on Friday instead.

The exchange, which now accounts for 22% of the whole market volume, updated the statement on Monday, blaming the weakness of bitcoin’s infrastructure for the withdrawal problems. That caused another drop in prices and prompted open criticism from the Bitcoin Foundation.

Mr. Burges was also unhappy with Monday’s statement, saying he believes “not enough information is disclosed.”

“I want get my bitcoin back, or get Mt.Gox to bring back public confidence that the company is solvent and people’s money are safe,” said the 40-year-old protester. He deposited 250 bitcoins, with a current value of around $99,000, into his Mt.Gox account in early January, intending to keep them there temporarily, an action he now regrets. He said he won’t use the exchange again.

Tokyo was blanketed in heavy snowfall on Friday morning, but that didn’t stop Mr. Burges’s protest action at Mt.Gox’s offices in Tokyo’s Shibuya district. Taking up position outside the building housing the offices at 8:45 a.m., he encountered Mr. Karpeles, showing up for work around 9:15, a cup from Starbucks in hand. He confronted the French executive, who was reluctant to answer his questions and soon managed to walk past him to get inside the building.

Another frustrated Bitcoin trader from Australia, who wished to remain anonymous, also staked out the Mt.Gox offices last week, managing to get some time with executives, though he said he wasn’t completely satisfied.

Meanwhile, worries about the state of investors’ accounts at Mt. Gox was a major topic of conversation at a Tokyo bitcoin community’s weekly meeting on Thursday at a restaurant just a five-minute-walk from the Mt.Gox office.

“We are requesting Mr. Karpeles to join the meet-up and offer us explanations,” an organizer of the meeting said. “But they hardly appear in public lately.”

In an email on Thursday, Reina Matsushita, a Mt.Gox spokeswoman, said the company would issue a statement later that day, but by Friday morning no new statement had appeared on the company’s website. Phone calls to the company’s office rang unanswered on Friday.

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